A House of Commons committee is to investigate the possible decriminalisation of cannabis and also address the Government's drug policy.

The powerful Home Affairs Committee will question whether current drug rules work in its first major inquiry of the new parliament.

Witnesses include key Government figures such as the Lord Chancellor Lord Irvine of Lairg and Home Secretary David Blunkett.

The committee will look at the effect of liberalisation on the availability and demand for drugs.

It will also study the effect of relaxing restrictions on drug–related deaths and crime.

The committee, which will meet in October, will also examine whether decriminalisation is desirable and if not, discuss "practical alternatives".

The move comes amid growing backbench calls, including from former Tory Cabinet minister Peter Lilley, for the liberalisation of cannabis laws.

The new committee will look at the effectiveness of the 10 year National Strategy on drug misuse and take into account the Police Foundation's report on drugs which was chaired by Dame Ruth Runciman.

Its chairman is former junior minister Chris Mullin who left the Government of his own accord after the election because he wanted to return to chairing the committee.

The issue arose earlier this month when Tory grandee Peter Lilley rocked die–hard traditionalists in the Conservative party with his call to legalise cannabis.

The former deputy leader of the Tory party envisaged magistrates issuing licences for outlets selling cannabis to over–18s.

Downing Street has firmly resisted any liberalisation of the drugs laws, although Mr Blunkett has said there should be an "adult, intelligent" debate on the issue.

Leading charity DrugScope today welcomed the inquiry as a valuable contribution to a more open and mature debate on drugs in the UK.

DrugScope director of communications Harry Shapiro said: "Last year's Police Foundation Inquiry gave the drugs debate a much–needed impetus.

"We have seen evidence in recent weeks that more politicians are ready to take on this complex issue and explore the possibilities for change.

"It is a subject which interests a large number of ordinary people and an open and mature debate could help re–engage many, particularly the young, in the political process."